Conventionally, in a vehicle such as a car, in a seal-type rolling bearing for use in a power transmission pulley, an electromagnetic clutch or the like used to transmit power to a compressor included in a refrigeration cycle, there are disposed a total of two contact seals (seal plates) one on either side thereof to thereby attain a sealed condition.
In each of the seal lips of the two-side seal plates, there is formed an air hole (or a slit) in at least one portion thereof in the circumferential direction thereof.
The reason for this is as follows: that is, in case where a contact seal bearing without air hole is incorporated, when the pressure of the interior of the bearing rises and lowers, the internal and external pressures of the bearing cannot be equalized, which incurs a fear that there can occur seal removal, seal lip adsorption phenomenon or the like; and, therefore, there is proposed a bearing in which, by escaping the air through the air hole to thereby equalize the pressure of the interior of the bearing with the pressure of the exterior thereof, the above-mentioned seal removal, seal lip adsorption phenomenon or the like can be prevented (for example, JP-UM-B-6-50655, JP-UM-A-6-73454, and the like).
However, in the conventional contact seal (seal plate) bearing having an air hole, when the bearing at a high temperature is drenched with water drawn in from outside and is thereby cooled suddenly (for example, when a vehicle passes through a puddle of water while it is running), the pressure of the interior of the bearing is lowered suddenly, so that, at the same time when the air is drawn in through the air hole, the water existing outside is also sucked in through the air hole, which reduces the life of the bearing outstandingly.
The present invention at eliminating the above-mentioned drawbacks found in the conventional bearings. Accordingly, it is an object of the invention to provide a seal-type rolling bearing which not only can secure a high seal sealing performance but also can equalize the pressure of the interior of the bearing with the pressure of the exterior thereof.